1. Field of the Invention
The invention is directed to compact power semiconductor modules, and, more particularly, to an arrangement in which a pressure piece exerts pressure on a printed circuit board to effect electrical and thermal contact in the module, while permitting the placement of electrical components on the face of a printed circuit board underneath the pressure piece.
2. Background of the Prior Art.
Modern designs for such power semiconductor modules with high power in proportion to their structural size, which are the point of departure of the present invention, are known from German Patent DE 196 30 173 C2 or German Patent DE 199 24 993 C2.
German Patent DE 196 30 173 C2 discloses a power semiconductor module for direct mounting on a heat sink, comprising a housing and an electrically insulating substrate which in turn comprises an insulator body with a plurality of metal connecting tracks, insulated from one another and located on the insulator body, and power semiconductor components located on the connection tracks and connected to these connection tracks with appropriate circuitry. The external electrical connection to a printed circuit board disposed outside the housing is accomplished by means of at least partly resilient connection leads.
The power semiconductor module furthermore has at least one centrally located recess through which a screw connection can pass. The screw connection serves, together with a dimensionally stable pressure piece disposed on the side of the printed circuit board remote from the power semiconductor module and resting flatly on the printed circuit board, to provide the pressure contact of the module. This pressure contact performs two tasks simultaneously: first, making secure electrical contact between the connection elements and the printed circuit board, and second, making thermal contact between the module and a heat sink, both kinds of contact being releasable.
A disadvantage of these known power semiconductor modules is that the known pressure piece does not allow further components, such as resistors, capacitors or integrated circuits, to be disposed on the part of the printed circuit board that is covered by the pressure piece.
German Patent DE 199 24 993 C2, for example, shows power semiconductor modules in which the connection elements are extended from the power semiconductor module to a printed circuit board in the form of soldered pins. These soldered pins serve as both control and load connection leads for electrically connecting the power semiconductor components within the power semiconductor to the supply lines disposed on the printed circuit board. Thus, the power semiconductor module can be connected either directly to a printed circuit board or, as disclosed in DE 199 24 993 C2, indirectly by means of an adapter board. The thermal contact between the power semiconductor module and a heat sink is established by means of screw connections, independent of the electrical contacts.
A disadvantage of the design of such power semiconductor modules is that integrating the module into a higher-order system requires the use of two different connecting techniques (screw and soldered connections), which must be accomplished in multiple manufacturing steps. A particular disadvantage here is that the contact security of the soldered connections is not assured over the service life, and that the soldered connection does not enable replacing the power semiconductor module except at significant effort and expense.